[tifosiman]

Ring and pinion.

A used set is worthless, because it would cost more than a used transmission to install them and get them shimmed properly.

Start looking for another good used trans, so that when this one goes, you will have a replacement. Go easy on it in the meantime, especially on 1st gear launches. If you launch hard when the gaps are lined up (where the missing tooth is), you will shear more in a rapid fashion and create some nice metal granola bits.

FYI, burnouts and hard-shifting are not the only culprits for r&p failure. There are other issues that contribute as well, including driving while having a bad clutch center, and lack of maintanence (r&p should be checked and re-shimmed at specified intervals).